Rust-preventing agent



:agents is already known. agents based on this principle is due to thedifferent bejhavior of metals which have a distant position with re-:spect to one another in the electromotive series. The

RUST-PREVENTING AGENT No Drawing. Application February 12, 1957 SerialNo. 639,622

Claims. (Cl. 106-14) The present invention relates to a rust-preventingagent, more particularly an agent of the kind consisting of pow- ,dersof metals having diiferent positions in the electro- ,motive series ofthe elements.

The use of metal powders for making rust-preventing The eifect of theanti-rust rust-preventing agent constitutes, as it were, a galvaniccell, by whose reducing action the metal to be protected is guardedagainst oxidation. One condition for bringing about this eflect is thealkaline adjustment of the agent, in order to accomplish a reversal ofthe metals as regards their position in the electromotive series. Inthis man ner, iron becomes the cathode and the other metals become theanode, so that the potential causing corrosion does not become active onthe iron, but on the metal powder, and is thereby made harmless.

Metal components of a coating of paint are protected by the addition ofcharcoal against moisture, vapors, acids and the like, since charcoalabsorbs the oxygen and gives off alkalies. Furthermore, charcoal aids inthe even suspension of the metal powders in a binder. Another purpose ofthe addition is its role as a pigment for obtaining a grey or blackcolored coat.

For alkaline adjustment, rust-preventing paints have already been madewith charcoal, which had previously been impregnated with alkali, e.g.potash or gaseous am monia. However, it has been discovered that theimpregnation with alkali often has certain disadvantages for anti-rustpaints. One of them is the occurrence of a certain saponification of thebinder, a second one the difficulty of maintaining a definitealkalinity, which depends on uncertain factors. If the degree ofalkalinity is changed, this may sometimes lead to a reversal in the polarity of the metals, so that the anti-rust paint would on the contraryact as a rust-promoing agent.

It is the object of the present invention to provide an anti-rust agentor paint, which is free of the above mentioned drawbacks and willprovide a safe protection of lasting effect. The necessary alkalinity isconstantly maintained by the chosen ingredients and, if necessary,re-adjusted.

For this purpose, a conventional binder, e.g. varnish, is compoundedwith powdered metals, on the one hand with iron, on the other hand witha second metal of the group consisting of magnesium, lead and zinc. Tothis mixture, powder of active carbon, having a large surface, is added,which has not been impregnated. The active carbon will therefore retainits absorptive capacity and will be capable of forming a buffer in thesystem, in which it will absorb the hydrogen which will be evolved.

In addition to the above mentionedingredients, the system contains ametal oxide of the second metal, in an amount ranging from 1 or 2, up to4% of the metal used.

The metal oxide is slightly alkaline, but the alkalinity does not becomeeffective on the binder; however, it is sufiicient to maintain therequired polarity.

Instead of using one other metal in addition to iron, a mixture of suchmetals may be used and, accordingly, a mixture of their oxides. Themetaloxide or oxides are continually regenerated by the oxygen evolved andthe metal present. The oxide or oxides act similar to a cataiyst. Thesystem formed is stable and resists washing out by water or moisture.The hydrogen absorbed by the active carbon is a reducing component whichalso acts as a protective agent for the iron.

The rust-resistive paint constitutes a system which automaticallyre-adjusts itself.

One definite advantage is the safety against reversal of the polarity,since the alkalinity is maintained as long as there is some metalpresent. It is impossible that the rust-resisting paint at one timebecomes a rust-promoting agent.

Paints as described above are particularly useful as marine paints foruse on hulls, decks, or bottoms of ships. A rinsing out of the alkalinecomponents by sea water cannot take place, as it was often experiencedwith paints hitherto in use, which were made with charcoal having alkaliabsorbed therein.

When using the paint for ship bottoms, it is advantageous to add copperas second metal or in addition to a second metal, such as lead,magnesium or zinc mentioned before. Copper and its oxide have the addedadvantage of preventing deposits of animal or vegetable matter.

The invention will now be more fully described in a number of examples,but it should be understood that these are given by way of illustrationand not of limitation and that many changes in the details can be madewithout departing from the spirit of the invention.

Example 1 The following components are mixed together:

120 kgs. linseed oil varnish kgs. powdered magnesium 30 kgs. powderediron 30 kgs. active charcoal, and

8 kgs. magnesium oxide As contrasted to methods used heretofore, heatingis not necessary, it should, on the contrary, be avoided. The mixture isready for use.

Example 2 The components mixed together are:

kgs. varnish acting as a binder 80 kgs. lead powder 32 kgs. iron powder40 kgs. charcoal, also as powder 4 kgs. PhD

7 Example 3 The following ingredients are mixed together:

100 kgs. varnish 62 kgs. lead powder 36 kgs. copper powder 32 kgs. ironpowder 40 kgs. active carbon 4 kgs. lead oxide 12 kgs. copper oxide WhatI claim is:

l. A coating composition having rust-preventing properties due to itscontent of metal powders having differing positions in the electromotiveseries of the elements, consisting of 100 to kg. of a varnish, 30 to 32kg. iron powder, 62 to 80 kg. of asecond polyvalent metal selected fromthe group consisting of magnesium, zinc, lead and a mixture of the same,as Well as 4 to 8 kg. of an oxide of the second metal, and containing 30to 40 kg. activated carbon. i i

2. The rust-preventive coating composition according to claim 1, for useas a shi p-bottom paint, containing, in addition to the ingredientsnamed, 36 kg. copper and 12 kg. copper oxide.

' 3. Arust-preventing composition according to claim 1, consisting of120 kgs. linseed oil varnish, 80 kgs. magnesium powder, 30 k gs. ironpowder, 30 kgs. activated carbon and 8 kgs. magnesium oxide.

4. A rust-preventing composition according to claim 1, consisting of 100kgs. varnish, 80 kgs. lead powder, 32

References Cited in the file of this patent FOREIGN PATENTS 435,003Great Britain Sept. 12, 1935 431,641 Great Britain July 10, 1935 563,653Great Britain Aug. 24, 1944

1. A COATING COMPOSITION HAVING RUST-PREVENTING PROPERTIES DUE TO ITSCONTENT OF METAL POWDERS HAVING DIFFERING POSITIONS IN THE ELECTROMOTIVESERIES OF THE ELEMENTS, CONSISTING OF 100 TO 120 KG. OF A VARNISH, 30 TO32 KG. IRON POWDER, 62 TO 80 KG. OF A SECOND POLYVALENT METAL SELECTEDFROM THE GROUP CONSISTING OF MAGNESIUM, ZINC, LEAD AND A MIXTURE OF THESAME, AS WELL AS 4 TO 8 KG. OF AN OXIDE OF THE SECOND METAL, ANDCONTAINING 30 TO 40 KG. ACTIVATED CARBON.